Recent years have witnessed ever increasing quantities of carbonated beverages, such as beer and carbonated soft drinks, being packaged in amounts up to 12 ounces in metal cans and particularly in metal cans with ends that include a score line defined opening panel therein to provide implement free access to the contents. Such opening panel containing can ends are generally called "easy open ends" and include variant basic constructions of a first type wherein the score line completely circumscribes the panel to render the panel completely separable from the can end and of a second type wherein the score line only partially circumscribes the panel to render the latter only partially severable from the can end and to thus remain in attached relation within the can end after the pouring opening has been formed. As mentioned above, such opening panels are conventionally perimetrically delineated by score lines of decreased metal thickness.
In order to extend the use of such easy open can end constructions to larger volume containers, the art has suggested the utilization of a cap assembly to close and reseal the opening defined by such score line defined panel. Among the objects of such cap utilization are a re-closure of the container to prevent loss of liquid content and resealing of the container to limit further losses of the dissociable gases, i.e., the "carbonation", in the remaining liquid contents. U.S. Pat. No. 4,580,692 discloses one construction for such a resealable closure cap assembly in association with a selectively contoured can end construction to cooperatively accommodate such resealable closure and to retain the advantages characteristic of the "easy open end" construction.
The provision of commercially acceptable resealable easy open can end constructions for larger capacity beverage containers requires, in addition to the functional features of present easy open can ends, both sealable retention of the can contents and accommodation by the resealed cap of the inherent pressure buildup therein. Also required is a can end configuration at the pouring opening to accommodate the disposition of a resealing cap in operative relation thereto without appreciable diminution of the convenience and cost effective nature of the basic easy open end constructions during manufacturing, filling, shipping, selling, and consumer usage. As such, the provision of a commercially acceptable resealable easy open end construction requires accommodation of problems not heretofore met in the basic easy open end constructions conventionally employed in the smaller capacity beverage cans.
Experience to date with the resealable cap and can end construction disclosed in U.S. Pat. Nos. 4,580,692 and 4,648,528, the disclosure contents of which are herein generally incorporated by reference, has indicated that eventual failure of the can end due to excessive internal pressure therein may result in rupture of the score line defining the opening panel in the pouring spout. This locus of failure is quite different from that of conventional easy open can end constructions, where, under excessive internal pressure, the end usually ruptures in the vicinity of the peripheral countersink when the countersink inverts. The current industry standard requires that the can end be of such character as to accommodate an internal pressure of 93 psi before the initiation of countersink buckling.